The present invention relates generally to snow plows for use with light and medium duty trucks, and more particularly to an improved snow plow having an impact-absorbing mechanism which absorbs the shocks of both the tripping of the snow plow blade upon striking an object and the spring-biased return of the snow plow blade to its original position.
Once the exclusive domain of municipality-operated heavy trucks, snow plows have been used with light and medium duty trucks for decades. As would be expected in any area of technology which has been developed for that period of time, snow plows for light and medium duty trucks have undergone tremendous improvement in a wide variety of ways over time, evolving to increase both the usefulness of the snow plows as well as to enhance the ease of using them. The business of manufacturing snow plows for light and medium duty trucks has been highly competitive, with manufacturers of competing snow plows differentiating themselves based on the features and enhanced technology that they design into their products.
When plowing snow, a not infrequent occurrence is striking an object which is concealed beneath the snow. This occurs particularly often when plowing roads which are not paved, such as, for example, gravel roads or dirt roads. Since roads being plowed are typically frozen, it is common for an object of significant size to become frozen into the road. For example, medium size rocks or sticks which would not present a significant obstacle were they loose on the surface of the road can present a problem when they are frozen into the surface of the road and concealed beneath a layer of snow. In addition, when significant snow depth covers the area being plowed, the operator may miscalculate and drive the snow plow into a fixed obstacle such as a curb.
For this reason, snow plow blades have for some time been manufactured with a blade trip mechanism which allows the bottom of the blade to yield upon substantial impact. This is typically accomplished through the mounting of the snow plow blade on its support structure using a pivoting mechanism. The snow plow blade is mounted onto the support structure at a position between eight and sixteen inches above the ground in a manner which permits the bottom of the snow plow blade to pivot back when an object is struck. Simultaneously as the bottom of the snow plow blade pivots back, the top of the snow plow blade will pivot forward.
This movement between the normal plowing position of the snow plow blade to the position in which the bottom of the snow plow blade pivots fully backward is referred to as blade tripping. The movement of the snow plow blade from the normal plowing position to the tripped position is resisted by two or more strong trip springs which are mounted behind the snow plow blade, typically running from positions near the top of the snow plow blade to the snow plow blade support structure. Even when the snow plow blade is in its normal plowing position, the trip springs are under tension. Accordingly, it will be appreciated that when the bottom of the snow plow blade is forced backward, the trip springs will provide a strong resistance to the movement, tending to absorb some of the force of the impact of the snow plow blade with the object which has been struck.
When the force which has caused the snow plow blade to trip is removed, the trip springs will cause the snow plow blade to return to the normal plowing position, also referred to as the xe2x80x9ctrip returnxe2x80x9d position. Since it will be appreciated that it is highly undesirable for the snow plow blade to move from the normal plowing position when plowing snow, the trip springs are quite strong. This strength will result in a significant impact between the snow plow blade and its support structure when it is returned to the trip return position. This impact it typically metal on metal, and can over time result in damage to the snow plow blade and/or the supporting structure. In addition, if the snow plow blade strikes a fixed obstacle with sufficient force, the movement of the snow plow blade from the normal plowing position to the tripped position can also result in a metal on metal impact which can, over time, result in damage to the snow plow blade and/or the support structure.
It is accordingly the primary objective of the present invention that it provide a mechanism for absorbing a substantial part of the impact of the snow plow blade as it reaches its fully tripped position when the snow plow blade strikes an object with sufficient force to drive it to the fully tripped position. It is a closely related objective of the snow plow blade trip impact absorber of the present invention that is also provide a mechanism for absorbing a substantial part of the impact of the snow plow blade as it is returned to its trip return position by the force of the trip springs. It is a further related objective of the snow plow blade trip impact absorber of the present invention that it minimize or eliminate the metal-on-metal impact which would otherwise occur both at the fully tripped position of the snow plow blade and at the trip return position of the snow plow blade.
It is another objective of the snow plow blade trip impact absorber of the present invention that it not interfere with the tripping movement, either as the snow plow blade is tripping, or as it is returning to its normal plowing position, except as the snow plow blade approaches its extreme positions. It is yet another objective of the snow plow blade trip impact absorber of the present invention that the impact-absorbing members be made of a material which is highly resistant to damage even when absorbing large shocks caused by substantial impacts. It is a still further objective of the snow plow blade trip impact absorber of the present invention that the impact-absorbing members be easily replaceable when their lifetime has been expended.
The snow plow blade trip impact absorber of the present invention must also be of a construction which is both durable and long lasting, and it should also require little or no maintenance to be provided by the user throughout its operating lifetime. In order to enhance the market appeal of the snow plow blade trip impact absorber of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the snow plow blade trip impact absorber of the present invention be achieved without incurring any substantial relative disadvantage.
The disadvantages and limitations of the background art discussed above are overcome by the present invention. With this invention, an impact-absorbing member is mounted at each pivot point used to support the snow plow blade from its support structure. The impact-absorbing member is mounted on the support structure, and is shaped such that it will be contacted by a part of the snow plow blade as the snow plow blade moves toward either its fully tripped position or its trip return position. The impact-absorbing member is made of a high density polymeric material such as polyurethane, which will absorb the impact to prevent or minimize metal-to-metal impact which would otherwise cause significant wear on the snow plow blade and/or its support structure.
In a typical embodiment, the snow plow blade is supported at two pivot points on the right and left sides of the snow plow blade by a swing frame. Trip springs mounted between the snow plow blade and the swing frame provide the tripping resistance force. The snow plow blade has a plurality of vertically oriented curved ribs which are connected between top and bottom plow frame members, and two of these ribs have apertures located between approximately eight and sixteen inches from the bottom of the snow plow blade. The swing frame has a pair of parallel blade pivot mounts located at each end thereof, which blade pivot mounts extend forwardly from a swing frame tube on which they are mounted.
Located near the front of each of the blade pivot mounts are apertures which are aligned in each pair of blade pivot mounts. Each pair of blade pivot mounts will receive a portion of one of the ribs on the snow plow frame which have the apertures therein, with one of the blade pivot mounts in each pair being located on either side of the rib to which that side of the swing frame is being mounted. A pin extends through the aligned apertures on each side of the snow plow blade to pivotally mount it on the swing frame.
Located between each pair of blade pivot mounts behind the rib of the snow plow blade received therein and in front of the swing frame tube is a pocket into which a cushion block will be placed. In the preferred embodiment, these pockets are further defined by additional support members which will prevent the cushion blocks from moving upwardly, downwardly, or rearwardly. Each cushion block is retained in its pocket between the pair of blade pivot mounts by a bolt which extends through apertures in the blade pivot mounts and the cushion block.
As mentioned above, the cushion blocks are made of a high density polymeric material such as polyurethane. The cushion blocks are configured so as to contact the ribs mounted to the blade pivot mounts before the snow plow blade reaches either the tripped position or the trip return position. The cushion blocks resemble a brick mounted in a vertical orientation, with the lower front having a corner removed therefrom. The polymeric material of which they are made is capable of absorbing a considerable impact, and is resilient and wear-resistant as well.
It may therefore be seen that the present invention teaches a mechanism for absorbing a substantial part of the impact of the snow plow blade as it reaches its fully tripped position when the snow plow blade strikes an object with sufficient force to drive it to the fully tripped position. The snow plow blade trip impact absorber of the present invention also provides a mechanism for absorbing a substantial part of the impact of the snow plow blade as it is returned to its trip return position by the force of the trip springs. In doing so, the snow plow blade trip impact absorber of the present invention minimizes or eliminates the metal-on-metal impact which would otherwise occur both at the fully tripped position of the snow plow blade and at the trip return position of the snow plow blade.
The snow plow blade trip impact absorber of the present invention does not interfere with the tripping movement, either as the snow plow blade is tripping, or as it is returning to its normal plowing position, except as the snow plow blade approaches its extreme positions. The impact-absorbing members of the snow plow blade trip impact absorber of the present invention are made of a material which is highly resistant to damage even when absorbing large shocks caused by substantial impacts. In addition, the impact-absorbing members of the snow plow blade trip impact absorber of the present invention are easily replaceable when their lifetime has been expended.
The snow plow blade trip impact absorber of the present invention is of a construction which is both durable and long lasting, and which will require little or no maintenance to be provided by the user throughout its operating lifetime. The snow plow blade trip impact absorber of the present invention is also of inexpensive construction to enhance its market appeal and to thereby afford it the broadest possible market. Finally, all of the aforesaid advantages and objectives are achieved by the snow plow blade trip impact absorber of the present invention without incurring any substantial relative disadvantage.